1. Field of the Invention
The present invention relates to the field of performance analysis and tuning, and more particularly, to the field of generating a frequency distribution representation, such as a histogram, using counter-based instrumentation.
2. Discussion of Related Art
For system performance tuning, it is helpful to be able to measure particular characteristics of the system to be tuned to see where improvements can be made. Two types of instrumentation have typically been used to measure various system characteristics: 1) counter-based instrumentation and 2) trace-based instrumentation.
Conventional counter-based instrumentation uses a single counter to count a number of events over a given sample period. This conventional counter-based instrumentation is typically small enough to be included on various types of integrated circuit devices such that it is possible to collect data from physically inaccessible (e.g. internal) signals. This approach presents a drawback, however, in that only average metrics, such as throughput, may be measured using a counter alone.
A different type of counter-based circuitry is described in co-pending U.S. patent application Ser. No. 08/768,913 to Kardach, filed on Dec. 17, 1996 and assigned to the assignee of the present invention (Attorney Docket Number 42390.P3689) ("the Kardach application"). The counter-based circuitry described in the Kardach application is capable of detecting bus utilization over a given sample period in order to determine whether to reset a standby timer. The counter-based circuitry of the Kardach application, however, does not provide for the generation of a frequency distribution representation of a particular metric across a particular variable range. Thus, the counter-based circuitry described in the Kardach application may have limited utility in the context of system performance tuning.
In contrast to counter-based instrumentation, trace-based instrumentation uses external hardware that is capable of probing the system to be measured, and collecting and storing long traces. Conventional trace-based instrumentation typically also includes some means for post-processing the collected traces into useful data and/or charts. More complex metrics, such as distributions across a variety of operating conditions, may be gathered using trace-based instrumentation versus counter-based instrumentation.
Trace-based instrumentation, however, can be expensive. A relatively large memory may be required to store the collected traces if the experiment is long, for example. Further, some of the signals that are desired to be measured may be physically inaccessible to external hardware.